How do you solve the system $2x-3y=21$ and $y=3-x$ using substitution?

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Answer 1 · 2017-03-03T08:05:00

$x=6$ & $y=-3$
Solution : $(6,-3)$

$2x-3y=21$ ------------(1)

$y=3-x$ -----------------(2)

Substituting eq 2 in eq 1

$2x-3(3-x)=21$

$2x-9+3x=21$

$5x-9=21$

$5x=30$

$x=6$

Put $x=6$ in eq 2 we get,

$y=3-6$

$y=-3$

Solution : $(6,-3)$

How do you solve the system 2x-3y=212x-3y=21 and y=3-xy=3-x using substitution?